The hydrodynamic model of Young et al. (1991) for external-loop gas-lift reactors was modified to account for buoyancy forces in the gas phase. The revised model is based on macroscopic balances for the gas-liquid separator and external downcomer and spatially-averaged, 1-D mass and momentum balances in the riser. Using only the physical properties of the gas and liquid phases, the reactor dimensions, and the gas superficial velocity, the model predicts gas holdup profiles, gas and liquid velocity profiles, and pressure profiles in the riser for bubbly flow. Empirical correlations are used to represent frictional and drag effects, but there are no adjustable parameters in the model. The system of equations that must be solved to predict hydrodynamic behavior is simpler than that of Young et al. The sensitivity of the model to choice of drag coefficient correlation is analyzed. The model predictions match experimental data of previous works.